Airbag modules can be classified into various types according to installation locations thereof. In this regard, types of airbag modules include steering wheel airbags, dashboard airbags, roof airbags, etc., and various airbag modules for each of the types have been introduced.
FIG. 1 shows an example of a roof airbag module 100 including an airbag cushion 110. Referring to FIG. 1, the roof airbag module 100 is installed on the inner surface of a roof 10 of a vehicle to protect a passenger 30 (FIG. 1 illustrates a dummy, which is used instead of a real passenger for experimenting airbag inflation) on the rear seat 20 of the vehicle.
When a signal indicating that the vehicle is in collision is detected, an inflator (not shown), which is disposed inside a housing 120 of the roof airbag module 100, injects gas into the airbag cushion 110, so that the airbag cushion 110 is deployed. The airbag cushion 110 includes a first chamber 111, which is deployed in a right-triangular shape having the hypotenuse facing toward the lower front (a direction between the X axis direction and −Y axis direction in FIG. 1), and a second chamber 112, which is deployed to protrude rearward of the first chamber 111 (the −X axis direction).
The second chamber 112 protrudes rearward to support the head 31 of the passenger 30 as soon as possible when the vehicle is in collision, without waiting until the head 31 is jerked forward. However, since there is a large opening 112a formed between the second chamber 112 and the first chamber 111, the first chamber 111 and the second chamber 112 do not function differently even momentarily so as to protect the passenger more efficiently.
As gas from the inflator diminishes and the airbag cushion 110 is pressed by the head 31 of the passenger 30, gas within the deployed airbag cushion 110 is exhausted to the outside via an vent hole 111a, and internal pressure of the airbag cushion 110, and more particularly, internal pressure of the first chamber 111 decreases.
In the airbag module 100 described above, the shape of the first chamber 111 is a right triangle extending downward, the vent hole 111a is positioned in front of the first chamber 111, and force is exerted frontward (X direction) onto the first chamber 111 by the passenger 30. Therefore, a middle portion F of the front portion (a portion corresponding to the hypotenuse of the right triangle) of the first chamber 111 close to the vent hole 111a is folded when the internal pressure decreases, and thus the passenger 30 cannot be supported for a sufficient time period. As a result, even if the airbag cushion 110 is deployed when a vehicle is in collision, a passenger, and more particularly, a passenger without a seatbelt on might not be protected sufficiently.